I haven't used mine in 3 1/2 years (will be 4 when baby is born in Nov), so I took it to the LC I used with DS, they hooked up a gauge to it (both sides) and verified that the psi was correct (actually a little above normal, which was fine) and I am good! So I say, take it to a Lactation Consultant's office, ask pediatrician if they can help too, some offices have LC's and they would have the tool needed...HTH